The invention relates generally to a method and apparatus for interacting with virtual objects in a haptic virtual reality environment, and more specifically to a method and apparatus for modifying virtual objects in a haptic virtual reality environment.
Computers have been long used to design objects in a computerized environment. Examples are CAD (computer-aided design) systems that are used in the design of mechanical parts, such as parts used in an assembly process. For example, a designer may use a CAD system to design parts for an automobile, which are then produced and used in an automobile assembly line. Such CAD systems require significant training and understanding in using the computerized design system. CAD systems are typically difficult to use and lack the freedom and expressiveness of traditional noncomputerized drawing, sketching, and model-making procedures.
One traditional noncomputerized approach is the blue foam technique. In this approach, a two-dimensional (2-D) cardboard template is made and attached to one side of a block of blue foam material. The designer uses a hot wire to trace out the shape of the template throughout the blue foam block and then removes the excess foam.
Another noncomputerized approach involves modeling the object from clay using a traditional sculpting approach based on hand tools and hand sculpting techniques to add, remove, and shape the clay.
These approaches suffer from traditional limitations such as the time needed to hand design templates, and the difficulty or inability to recover from mistakes or return to a previous stage of design. Objects created using traditional physical modeling methods cannot be directly incorporated or used in modem digital CAD and computer-aided manufacturing (CAM) processes. In addition, blue foam and clay approaches cannot be combined readily in the same model.
A more modem approach uses a virtual reality technique to model objects in a computerized virtual environment. Virtual Reality (VR) is an artificial environment constructed by a computer which permits the user to interact with that environment as if the user were actually immersed in the environment. Early VR devices permitted the user to see three-dimensional (3-D) depictions of an artificial environment and to move within that environment. The reality of the VR environment is enhanced by the ability of a user to manipulate virtual objects within the virtual environment using hand motions and gestures. A user may use a virtual tool to manipulate and/or modify a computerized model or virtual object in the virtual environment.
Virtual reality techniques often do not provide for a realistic feeling of sculpting by the user. The user cannot feel when virtual tools touch or modify the virtual object. Moreover, in some cases, the virtual tool may pass through the virtual object without any impediment, thereby severely degrading the realism of the experience and the user""s ability to finely control the modification.
Thus, there is a need for a 3-D computerized modeling system that overcomes the problems of CAD techniques and traditional noncomputerized modeling techniques. One object of the present invention is to provide a computerized 3-D virtual reality modeling system that provides the ease and expressiveness of traditional sketching, drawing, and hand model-making approaches as well as integration into the digital design and manufacturing process offered by CAD/CAM techniques
Being able to feel the virtual object allows the user to resolve visual ambiguities, such as a shape that may appear either concave or convex as perceived by an observer. The user may rely on haptic feedback when modifying the object such as scratching a slight groove in the object, which the user then deepens or expands while receiving feedback through the tool on the shape and current depth of the groove. Feedback also allows the designer to monitor and modulate the cutting rate or amount of change induced by the virtual tool. Haptic feedback also helps the user navigate around and on the surface of the object; that is, using the feel of the object to know where the virtual tool is on the object.
The invention also relates to a method for modifying a virtual object in a haptic virtual environment, including sensing a location of a user in real space; determining a virtual tool comprising discrete points for use by the user in the haptic virtual environment; producing a mirrored virtual object by mirroring an initial portion of the virtual object to generate two mirrored portions; determining the locations of the discrete points of the virtual tool relative to a selected one of the two mirrored portions of the mirrored virtual object; calculating an interaction force based on the locations of the discrete points of the virtual tool and the location of the selected portion of the mirrored virtual object; and modifying the selected portion of the mirrored virtual object based on the locations of the discrete points of the virtual tool and the location of the selected portion of the mirrored virtual object.